Tunable Artificial Dielectrics

ABSTRACT

Tuning devices and methods are disclosed. One of the devices comprises a metal structure connected with artificial dielectric elements, and variable capacitance devices. Each variable capacitance device is connected with a respective artificial dielectric element and with a control signal. Control of the variation of the capacitance allows the desired tuning. Another device comprises metallic structures connected with artificial dielectric elements and switches connected between the artificial dielectric elements. Turning ON and OFF the switches allows the capacitance between artificial dielectric elements to be varied and a signal guided by the metallic structures to be tuned.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of provisional application60/705,870 for “On-Chip Tunable Artificial Dielectrics Based VCO” filedon Aug. 4, 2005, provisional application 60/705,871 for “On-chip TunableArtificial Dielectrics” filed on Aug. 4, 2005, and provisionalapplication 60/794,012 for “On-Chip Tunable Artificial Dielectrics”filed on Apr. 21, 2006, all of which are incorporated herein byreference in their entirety.

GOVERNMENT INTEREST

The invention was made with Government support of Grant No.N66001-04-1-8934, awarded by the U.S. Navy. The Government has certainrights in this invention.

BACKGROUND

1. Field

The present disclosure relates to tunable circuits, devices and methods.In particular, it relates to tunable artificial dielectrics.

2. Description of Related Art

Artificial dielectrics are known in the art and are made, for example,by distributing small polarizable particles in a uniform backgroundmaterial and represent a macroscopic analogue of a natural dielectrics.The polarizable particles can be either metallics particles ordielectric particles. Reference can be made, for example, to R. E.Collin, “Field Theory of Guided Waves” 2^(nd) Edition, pp. 749-786, IEEEPress, New Jersey, 1990 or W. E. Kock, Metallic Delay Lenses, BellSystem Tech. J., Vol. 27, pp. 58-82, 1948. Those two papers areincorporated herein by reference in their entirety.

Known artificial dielectric materials are, for example, discrete orfloating metal spheres, disks, strips or rods, etc. When embedding thesematerials into an electromagnetic field, the artificial particles ofthese materials are polarized by the applied field, with the positiveand negative charges displaced from each other. Each particle then actsas a dipole, contributing to the total charge displacement and thus toan effective dielectric constant.

FIG. 1 shows a plurality of floating metal sheets 1, where the positiveand negative charges 2, 3 of each metal sheet are displaced from eachother under the influence of an applied field E. The electromagneticfield polarized dipoles act as the artificial dielectrics.

A device based on the artificial dielectrics concept is shown, forexample, in W. Andress and D. Ham, “Standing Wave Oscillators UtilizingWave-Adaptive Tapered Transmission Lines,” Symposium on VLSI CircuitsDigest of Technology Papers, pp. 50-53, 2004, where an artificialdielectrics based standing wave oscillator is disclosed.

Further, wavelength or frequency tunability is important for radiofrequency (RF), microwave and millimeter wave components and circuits.It can be used to tune the working frequencies of components, such astransmission lines, resonant tanks, antennas, delay lines, filters,inductors, transformers, baluns, duplexers and circuits, such asamplifiers, mixers, filters, VCOs, PLLs and any other circuits thatemploy wavelength or frequency or tuning filtering.

SUMMARY

The present disclosure addresses the above described two concepts in anovel and original manner.

According to a first aspect, a device is disclosed, comprising: aplurality of artificial dielectric elements; a metal structure coupledwith the plurality of artificial dielectric elements; and a plurality ofvariable capacitance devices, each variable capacitance device having afirst end connected with a respective artificial dielectric element ofthe plurality of artificial dielectric elements, and a second end;wherein each second end is adapted to be connected to a control signal,the control signal controlling variation of the capacitance of thevariable capacitance devices.

According to a second aspect, a voltage controlled oscillator isdisclosed, comprising: a metallic structure to guide an input wave; aplurality of artificial dielectric elements connected with the metallicstructure, the input wave polarizing metal particles in the artificialdielectric elements; and variable capacitance devices, each having afirst end connected with a respective artificial dielectric element, anda second end adapted to be connected with a control signal, the secondends of the variable capacitance devices forming a control input of thevoltage controlled oscillator to control the frequency of the inputwave.

According to a third aspect, a method for tuning a signal is disclosed,comprising: coupling a metal structure with a plurality of artificialdielectric elements, the metal structure adapted to guide the signal tobe tuned; providing a plurality of variable capacitance devices, eachvariable capacitance device having a first end connected with arespective artificial dielectric element of the plurality of artificialdielectric elements, and a second end; connecting each second end to atleast one control signal; and tuning the signal by varying thecapacitance of the variable capacitance devices through the at least onecontrol signal.

According to a fourth aspect, a device is disclosed, comprising: a firstand a second plurality of artificial dielectric elements; a firstmetallic structure coupled with the first plurality of artificialdielectric elements; a second metallic structure coupled with the secondplurality of artificial dielectric elements; and a plurality ofswitches, each switch connected with a respective artificial dielectricelement of the first plurality of artificial dielectric elements and arespective artificial dielectric element of the second plurality ofartificial dielectric elements, each switch further connectable with acontrol signal, the control signal tuning the frequency of a signalguided by the first and second metallic structures.

According to a fifth aspect, a device is disclosed, comprising: aplurality of artificial dielectric elements; a metallic structurecoupled with the plurality of artificial dielectric elements; aplurality of switches, each switch having a first terminal connectedwith a respective artificial dielectric element of the plurality ofartificial dielectric elements, a second terminal connected with ground,and a third terminal connectable with a control signal, the controlsignal tuning the frequency of a signal guided by the metallicstructure.

According to a sixth aspect, a switch controlled oscillator (SCO)comprising the device of the fourth or fifth aspect is disclosed.

According to a seventh aspect, a resonator comprising a plurality ofdevices according to the fourth or fifth aspect connected in a closedloop arrangement is disclosed.

According to an eighth aspect, a transmission line comprising a deviceaccording to the fourth or fifth aspect is disclosed.

According to a ninth aspect, a switch controlled reconfigurable filtercomprising the device of the fourth or fifth aspect is disclosed.

According to a tenth aspect, a synthesizer is disclosed, comprising: avoltage control oscillator (VCO); a transmission line connected to theVCO, the transmission line having a transmission line input and atransmission line output; a mixer adapted to mix a signal on thetransmission line input with a signal on the transmission line output,the mixer having a mixer output; and a low pass filter connected withthe mixer output, the low pass filter having a low pass filter outputconnected with the VCO, wherein the transmission line is a transmissionline comprising a device in accordance with the fourth or fifth aspect.

According to an eleventh aspect, a delay locked loop (DLL) device isdisclosed, comprising: a voltage control oscillator (VCO); atransmission line connected to the VCO, the transmission line having atransmission line input and a transmission line output; a mixer adaptedto mix a signal on the transmission line input with a signal on thetransmission line output, the mixer having a mixer output; a low passfilter connected with the mixer output, the low pass filter having a lowpass filter output; a control logic block connected with the low passfilter output, the control logic block having a control logic blockoutput; wherein the transmission line is a transmission line comprisinga device in accordance with the fourth or fifth aspect.

The teachings of the present disclosure can be used to tune workingfrequencies of components, such as transmission lines, resonant tanks,antennas, delay lines, filters, inductors, transformers, baluns,duplexers and circuits, such as amplifiers, mixers, filters, VCOs, PLLsand/or any other circuits that employ wavelength or frequency tuning orfiltering.

High effective dielectric constants can be achieved, which is highlydesirable in integrated circuits because of the small size of passivecomponents.

The teachings of the present disclosure are compatible with main streamIC processes that comprise multiple metal layers, such as CMOS, BiCMOS,bipolar and SiGe technologies.

A large linear dynamic/tuning range can be obtained due to the largedielectric constant tuning range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, already discussed above, is a schematic diagram showing thegeneral concept of artificial dielectrics.

FIG. 2 shows an electric equivalent diagram of FIG. 1.

FIG. 3 shows an embodiment of a structure in accordance with the presentdisclosure.

FIGS. 4A-4D show examples of tunable artificial dielectrics.

FIGS. 5A-5C show open-circuited voltage coupled excitation circuits fora tunable artificial dielectrics standing wave resonant tank VCO inaccordance with the present disclosure.

FIGS. 6A and 6B show VCO phase noise comparison diagrams.

FIG. 7 is a diagram showing a Q-factor obtainable in accordance with thepresent disclosure.

FIG. 8 schematically shows a MOS transistor and a switch symbol.

FIG. 9 shows an embodiment of the present disclosure making use of theMOS transistor of FIG. 8.

FIG. 10 shows an electric equivalent circuit of the enlarged section ofFIG. 9.

FIG. 11 shows a further embodiment of the present disclosure.

FIG. 12A shows a differential quarter-wavelength standing-wavetransmission-line resonator based switch controlled oscillator (SCO).

FIG. 12B shows a simulation diagram related to the embodiment of FIG.11A.

FIG. 13 shows a traveling-wave transmission-line resonator.

FIG. 14 shows a transmission line based on the teaching of the presentdisclosure.

FIGS. 15A-15D show simulated phase shift results with reference to theembodiment of FIG. 14.

FIGS. 16A-16D show characteristic impedances of two differenttransmission line structures.

FIGS. 17A and 17B show an embodiment of a switch controlledreconfigurable filter (SCRF) in accordance with the present disclosure.

FIGS. 18A and 18B show application of transmission lines in accordancewith the present disclosure to phase-locked loop (PLL) and delay-lockedloop (DLL) devices.

DETAILED DESCRIPTION

FIG. 2 is an electric equivalent diagram of FIG. 1, where parasiticcapacitances 4 among the particles of the metal sheets 1 are shown. Theelectromagnetic wave creating the applied field is typically guided bymetallic structures 5, such as transmission lines, resonant tanks,antennas, inductors and transformers, and propagates through theartificial dielectrics, as shown in FIG. 2.

Variation of the parasitic capacitances 4 modifies the artificial dipoledistribution or the permittivity (capacitance ratio) as seen by theelectromagnetic wave of the applied field, which in turn changes thewavelength of the applied field accordingly.

The applicants have noted that variation of capacitance between theelements forming the allows the frequency of an applied signal to betuned. In particular, the present disclosure discloses a way of changingthe permittivity that characterizes the effect of dipoles in artificialdielectrics.

According to a first embodiment of the present disclosure, in order totune the dielectric constant, variable capacitance devices, such asvaractors and diodes, are used such that one end of each variablecapacitance device is connected to one of the artificial particles, andthe other ends of all capacitance devices (or all in a group) are tiedtogether and connected to control signals.

FIG. 3 shows an embodiment of a structure in accordance with the presentdisclosure, where two groups of variable capacitance devices are shown,for exemplary purposes. The schematic diagram of FIG. 3 shows aplurality of artificial particles (e.g. floating metal sheets) 1 and ametallic structure 5 to guide electromagnetic waves as already discussedwith reference to FIG. 3 above. Also shown in FIG. 3 are variablecapacitance devices 20 connected with the metal sheets 1. A first end ofeach variable capacitance device 20 is connected to a respective metalsheet 1. A second end of each variable capacitance device or a secondend of each group of variable capacitance devices is connected to acontrol signal. In this respect, FIG. 3 shows control signals CS 1 andCS 2.

The enlarged section 6 of FIG. 3 shows an artificial particle (e.g. afloating metal sheet) 1 and a variable capacitance device 7. The device7 can be, for example, a variable capacitance diode (varactor). A firstend 8 of the variable capacitance device 7 is connected to the particle1. A second end 9 of the variable capacitance device 7 is connected to acontrol signal. As shown in the embodiment of FIG. 3, the second ends ofa first group of variable capacitance devices are connected to a firstcontrol signal (Control Signal 1), while the second ends of a secondgroup of variable capacitance devices are connected to a second controlsignal (Control Signal 2). The person skilled in the art will devisealternative embodiments, where a single group (connection to a singlecontrol signal) or multiple groups of variable capacitance devices(connections to multiple control signals) are provided. The enlargedsection 6 of FIG. 3 also shows parasitic parameters, such as a parasiticcapacitance 10 and parasitic resistances 11, 12. The value of the totalvariable capacitance 20 connected to every artificial particle 1 isdetermined by the capacitive equivalent of a combination between thevariable capacitance 7 and all parasitic parameters.

Variation of the control signals (e.g., Control Signal 1 and ControlSignal 2 in FIG. 3) changes the capacitance 20 connected to each of theartificial particles 1, and thus has an effect on the permittivity ofthe artificial medium due to capacitance changes in the variablecapacitance devices 20. As a result, the wavelength of the wave speed ofthe electromagnetic wave guided by the metal structures becomes tunable.

Differential topologies are preferred for the metal structures to guidethe electromagnetic wave due to the presence of a virtual ground, whichprovides a well defined signal return path for the two branches ofdifferential structures and thus confines the electromagnetic fieldwithin the artificial dielectrics.

FIGS. 4A and 4B show a first example of a tunable artificial dielectricsacting as a standing wave resonant tank and comprising a metal structurehaving a first branch 31 and a second branch 32, together with aplurality of artificial dielectric elements 33 coupled with the branches31 and 32. In the embodiment of FIG. 4B, the dielectric elements 33 canbe smaller strips, distributed in a staggered configuration. Theelements 33 can be located on one or more levels. FIGS. 4A and 4B showstrips 33 located on two different levels. The person skilled in the artwill understand that strips having various dimensions and located onvarious levels can be provided. Usually, the higher the number of levelsthe more the electromagnetic field can be isolated from penetration intothe lossy silicon substrate under the elements. The metallic structureis located at a distance from the artificial dielectric elements. Thedistance (gap) between the metallic structure and the artificialdielectric elements can be in the order between 0.3 μm to few microns,depending on the processes. However, modern deep sub-micron technologiescan be used, to obtain a gap as small as 0.12 μm. Generally, the smallerthe gap the better the polarization of the artificial dielectricelements.

FIGS. 4C and 4D provide a second example of tunable artificialdielectrics acting as a standing wave resonant tank, comprising aU-shaped metal structure 40 with branches 41 and 42, together with aplurality of artificial particles 43. Also in this case, strips havingvarious dimensions and located on various levels can be provided.

Tunable artificial dielectric tanks like the ones shown in FIGS. 4A and4B usually have an open-circuited end and a short-circuited end.Therefore, the external (active) circuits which sense the standing wavesignal in the tank and compensate the loss of the tank may have eitheropen-circuited or short-circuited interfaces. Standing wave tanks havethe highest voltage signal at the open-circuited end and the largestcurrent signal at the short-circuited end. It is preferable not to drawtoo much energy from the tank when connecting circuits to the tank. Inorder to do that, voltage coupling should be used between open-circuitedends between tanks and circuits, and current coupling should be usedbetween short-circuited ends between tanks and circuits.

FIGS. 5A-5C provide examples of open-circuited voltage coupledexcitation circuits for a tunable artificial dielectrics standing waveresonant tank VCO in accordance with the present disclosure.

Some of the advantages of the circuit of FIGS. 4A and 4B are: Indirectlytuning the VCO frequency by varying the wavelength or wave speed. As aresult, frequency tuning effects are accomplished in light of theisolating tuning mechanism from the positive feedback loop used inconventional oscillators, resulting in much less noise;

Isolating the signal (i.e. the electromagnetic wave) from the substrateswhich, in silicon processes, are very noisy and lossy;No loss in the artificial dielectrics because no current flows in theartificial particles;High Q-factor due to the isolating substrate mechanism and losslessartificial dielectrics;High effective dielectric constants can be achieved, which is highlydesirable in integrated circuits because of the small size of passivecomponents;Compactable with main stream IC processes that comprise multiple metallayers, such as CMOS, BiCMOS, bipolar and SiGe technologies;Large linear frequency tuning range due to a large dielectric constanttuning range.

The teachings of the present disclosure allow to accomplish frequencytuning effects which result in much less noise when compared toconventional tunable resonant tanks, such as LC tanks.

FIGS. 6A and 6B show a VCO phase noise L(f) comparison between thetunable dielectrics in accordance with the present disclosure (FIG. 6A)and a conventional LC tank (FIG. 6B). FIG. 6B shows control signal noiseinduced phase noise signal portions 50 which are not present in thediagram of FIG. 6A.

The teachings of the present disclosure allow the signal (i.e. theelectromagnetic wave) to be isolated from the substrates, which are verynoisy and lossy in silicon processes. Additionally, there is no loss inthe artificial dielectrics, because no current flows in the artificialparticles. In view of the above advantages, a high Q-factor is obtained,as shown in FIG. 7. Such Q-factor can be very high even in commercialCMOS processes at frequencies as high as 60 GHz.

According to a further embodiment of the present disclosure, an embeddedartificial dielectric can be realized in MOS or CMOS technology withadaptive permittivity controlled by MOS or CMOS switches to achievefrequency synthesis/tuning/hopping, phase shift/delay, dynamic impedancematching and bandpass filtering over broad frequency ranges inreal-time.

In particular, the applicants have noted that variation of the effectivecapacitance (or permittivity) of an embedded artificial dielectric byusing shunt CMOS variable capacitors (varactors) can be limited by thefrequency tuning range which is inversely proportional to the dielectricboost factor defined in Eq. (1).

$\begin{matrix}{\frac{\Delta \; f}{f} = {{{- \frac{1}{2}}\frac{\Delta \; C^{\prime}}{C^{\prime}}} = {{- \frac{1}{2}}\frac{\Delta \; C_{v}}{{\kappa \; C} + C_{v}}}}} & (1)\end{matrix}$

where κC is the equivalent capacitance for the artificial dielectric,C_(v) is the total capacitance of the varactors, and ΔC_(v) is themaximum capacitor tuning range. When a large boost factor (k=22) isimplemented to reduce the on-chip resonator size, the maximum tuningrange is reduced to less than 5%.

To overcome the difficulty in reaching broadband frequency tuning inmodern software radios, a further embodiment to control the permittivityof the embedded artificial dielectric provides for insertion of MOSswitches.

FIG. 8 shows a MOS transistor and a switch symbol. The MOS transistorcomprises two connecting terminals (source S and drain D) and onecontrolling terminal (gate G). The body B of the MOS transistor isusually connected to ground.

FIG. 9 shows differential metallic structures 81, 82 coupled with aplurality N of metal strips (or, more generally, artificial particles)83, 84. As already previously discussed, the metallic structures 81, 82guide the wave while the N floating metal strip pairs 83, 84 serve asfloating conducting obstacles of artificial dielectrics. The arrangementof FIG. 9 also shows connection to a plurality of MOS switches 85 asshown in the enlarged portion of FIG. 9. In particular, each metal stripcouple 83, 84 is connected to the source S and drain D, respectively, ofa MOS switch, while the control signal is adapted to be connected to thegate G of the MOS switch 85.

FIG. 10 shows an electric equivalent circuit of the enlargement of FIG.9, with the switch ON (top portion of FIG. 10) or the switch OFF (bottomportion of FIG. 10).

FIG. 11 shows a further embodiment, where a metallic structure 101 iscoupled with a plurality of metal strips 102. The arrangement of FIG. 11also shows connection to a plurality of MOS switches 103 as shown in theenlarged portion of FIG. 11. In particular, each metal strip 102 isconnected to the drain D of a MOS switch 103, the source S of the switchbeing connected to a ground plane 104. Also in this case, the controlsignal (a digital control signal, for example) is connected to the gateG of the switch 103.

In both embodiments, when all MOS switches are turned on, the artificialdielectric reaches its highest permittivity and achieves boost-factorgiven by

$\begin{matrix}{\kappa = {\frac{ɛ^{\prime}}{ɛ} = {\frac{C^{\prime}}{C} = \frac{C + C_{AD}}{C}}}} & (2)\end{matrix}$

where C′ and C are the respective unit volume capacitance with andwithout the embedded artificial dielectric. And CAD is the sum ofincremental capacitances generated by N floating strips of the embeddedartificial dielectric, which can be expressed as

$\begin{matrix}{C_{AD} = {\sum\limits_{n = 1}^{N}C_{n}^{\prime}}} & (3)\end{matrix}$

where C′_(n) is the n'th incremental capacitance contributed by adifferential metal strip pair. For calculation purposes, see also R. E.Collin, “Field Theory of Guided Waves” 2^(nd) Edition, pp. 749-786, IEEEPress, New Jersey, 1990 and D. Huang, W. Hant, N.-Y. Wang, T. W. Ku, Q.Gu, R. Wong and M. F. Chang, “A 60 GHz CMOS VCO Using On-Chip Resonatorwith Embedded Artificial Dielectric for Size, Loss and Noise Reduction,”ISSCC Digest of Technical Papers, pp. 314-655, February 2006.

On the other hand, when each CMOS switch is turned off, it disconnectsthe metal strip pair and forbids the charge exchange between them.Effectively, this renders the C′_(n) to zero if neglecting the parasiticcapacitance. Therefore, by turning selective MOS switches on and offwith a programmable digital controller, the permittivity or theequivalent boost factor of the artificial dielectric can be varied to avery large range (from 1 to k) and with very fine resolution Δk of

$\begin{matrix}{{{\Delta\kappa}(n)} = \frac{C_{n}^{\prime}}{C}} & (4)\end{matrix}$

This results in a digital-controlled effective permittivity, ∈′ whichenables variable transmission wavelength with i th switch turned-on andj th switch turned-off as,

$\begin{matrix}{\lambda_{DiCAD} = \frac{\lambda}{\sqrt{1 + {\sum\limits_{{{n = i};} \neq j}^{N}{\Delta \; {\kappa (n)}}}}}} & (5)\end{matrix}$

where λ_(DiCAD) and λ are the effective wavelength with and withoutartificial dielectrics.

The applicants have called the techniques of the present disclosureDigital Controlled Artificial Dielectric as DiCAD. DiCAD has manypotential applications in modern multi-band software radio systems,including:

Switch Controlled Oscillator (SCO)

FIG. 12A shows a differential quarter-wavelength standing-wavetransmission-line resonator based SCO with embedded DiCAD. Thedifferential resonator, say for 60 GHz oscillation, is made of a one-endshorted co-planar strip 111 with a length of L=320 μm, a width of W=15μm and a gap of S=10 μm. 320 pairs of 1 μm metal strips 120 with gapsize of 1 μm are evenly placed underneath the transmission line forserving as the artificial dielectric. The connectivity of the metalstrip pair 111, 112 is controlled by the inserted NMOS switch 113 asdescribed previously. By selectively turning the NMOS ON or OFF (by wayof a digital control bit 121, for example), a very broad frequencytuning range (over 20 GHz) can be achieved simultaneously with very finetuning step of 80 MHz as indicated in the simulation of FIG. 12B. Inparticular, FIG. 12B shows four frequency spectra where, from left toright: the first one is obtained with all switches ON, the second one isobtained with one switch OFF and the remaining switches ON, the thirdone is obtained with two switches OFF and the remaining switches ON, andthe fourth one is obtained with all switches OFF.

The circuit of FIG. 12A comprises a shorted circuit end 114 and an opencircuit end 115, 116. As already explained with reference to a tankembodiment, the shorted circuit end forms a standing wave resonator,while the open-circuit end is connected to an excitation network 117which provides gain or negative resistance-R to compensate for resonatorloss.

In addition, similar tuning range and resolution can be achieved from atraveling-wave transmission-line resonator as indicated in FIG. 13. Theactive negative resistor-R shown in FIG. 13 compensates for transmissionlosses. Traveling-wave transmission-line resonators are known as such.See, for example, J. Wood, T. C. Edwards and S. Lipa, “RotaryTraveling-Wave Oscillator Arrays: A New Clock Technology,” IEEE JSSC,Vol. 36, No. 11, November 2001. FIG. 13 shows an embodiment with fourartificial dielectrics devices. Further embodiments can also be providedwith a different number of devices (e.g. 2, 3, 5 etc.) so long as aclosed loop is obtained.

Switch Controlled Phase Shifter (SCPS)

The propagation constant of a transmission line with embedded DiCAD isgiven by

$\begin{matrix}{\beta = \frac{2\pi}{\lambda_{DiCAD}}} & (6)\end{matrix}$

For a transmission line with a fixed length, changing electromagneticthe wavelength λ changes the electrical length or phase delay from oneend to the other end of the transmission line.

FIG. 14 shows a DiCAD based transmission line that can shift the phaseof an output signal and change the characteristic impedance Z₀ of atransmission line according to the digital control bits. Therefore, theembodiment of FIG. 14 allows phase delay and characteristic impedance ofa transmission line to be controlled. The working principle of theembodiment of FIG. 14 is the same as described in the previous figuresand will not be discussed here in detail.

FIGS. 15A-15D show the simulated phase shift results of the DiCADdescribed in FIG. 14 with both end terminated with a 50Ω load. The phaseis a linear function of the length of the transmission line. FIG. 15Ashows the phases of the output signal versus frequency with all switchesturned OFF and ON. The frequency of point m9 is 60 GHz. The phase ofpoint m9 is −53.58 deg. The frequency of point m10 is 60 GHz. The phaseof point m10 is −96.57 deg. FIG. 15B shows the phase difference betweenall switched OFF and ON versus frequency. The phase difference is alinear function of the frequency. The frequency of point m11 is 60 GHz.The phase difference at that point is −42.990 deg. FIG. 15C plots theoutput phase with one switch and two switches OFF versus frequency. Withthis structure under simulation, a linear total phase shift of 43° and aphase shift step of 0.07° are achieved at 60 GHz. The signal attenuationis less than 0.8 dB. FIG. 15D shows a phase difference or phase stepbetween one and two differences turned OFF versus frequency.

Switch Controlled Variable Impedance (SCVI)

The characteristic impedance of a transmission line with embeddedartificial dielectric is given by

$\begin{matrix}{Z_{0} = \sqrt{\frac{L}{C_{DiCAD}}}} & (7)\end{matrix}$

where L and C_(DiCAD) are the inductance and the capacitance of the unitlength of the transmission line respectively.

FIGS. 16A-16D show the characteristic impedances of two DiCADtransmission line structures. Structure one (FIGS. 16A and 16B) is thesame as that used in the above SCO and phase shift designs. Point m1 inFIG. 16A has a frequency of 60 GHz and a real part of characteristicimpedance real(Z0)=79.6 Ohm. Point m2 in FIG. 16A has a frequency of 60GHz and an imaginary part of characteristic impedance imag(Z0)=−1.3 Ohm.Point m1 in FIG. 16B has a frequency of 60 GHz and a real part ofcharacteristic impedance real(Z0)=44.4 Ohm. Point m2 in FIG. 16B has afrequency of 60 GHz and an imaginary part of characteristic impedanceimag(Z0)=−0.8 Ohm. In structure two (FIGS. 16C and 16D), L=536 μm (whereL is the length of the metallic structures), W==5 μm (where W is thewidth of the metallic structures) and S=10 μm (where S is the spacingbetween the two metallic structures). Point m1 in FIG. 16C has afrequency of 60 GHz and a real part of characteristic impedancereal(Z0)=114.86 Ohm. Point m2 in FIG. 16C has a frequency of 60 GHz andan imaginary part of characteristic impedance imag(Z0)=−2.97 Ohm. Pointm1 in FIG. 16D has a frequency of 60 GHz and a real part ofcharacteristic impedance real(Z0)=81.86 Ohm. Point m2 in FIG. 16D has afrequency of 60 GHz and an imaginary part of characteristic impedanceimag(Z0)=−2.15 Ohm. 45% and 30% of characteristic impedance tuning overa wide bandwidth are obtained with structure one and two, respectively.

Switch Controlled Reconfigurable Filter (SCRF)

Fixed frequency/bandwidth bandpass or bandstop filters were implementedin the past by using dual lattice constant (spacing) frequency selectivedistributed Bragg reflector on PCB. See, for example, T.-H. Wang and T.Itoh, “Compact Grating Structure for Application to Filters andResonators in Monolithic Microwave Integrated Circuits,” IEEE Trans onMTT, Vol. MTT-35, No. 12, December 1987. By using DiCAD transmissionlines on CMOS, lattice constants d_(A) and d_(B) can be reconfigured bydigitally controlling DiCAD switches on or off, to vary the bandpass orbandstop filter characteristics, as shown in FIGS. 17A and 17B. Thisre-configurable filtering structure has compact size, low insertion lossand ultra widely tunable bandwidth and center frequency.

Switch Controlled PLL/DLL

FIGS. 18A and 18B show the application of DiCAD embedded transmissionlines to synthesizers, such as a phase-locked loop (PLL) (FIG. 18A) anda delay-locked loop (DLL) (FIG. 18B).

With reference to the PLL of FIG. 18A, a voltage controlled oscillator(VCO) 181 is connected to a transmission line 182. The VCO 181 can be aconventional VCO or a switch controlled oscillator (SCO) as described inFIG. 12A. The transmission line 182 is a λ/4 transmission line alreadydescribed with reference to FIG. 14. The input 183 and the output 184 ofthe transmission line 182 are mixed in a mixer 185, the output of whichis fed to a low pass filter 186 and a charge pump 187 connected to theVCO 181. The mixer 186, low pass filter 186 and charge pump 187 formpart of the feedback loop of the PLL. The output 188 forms thephase-locked output of the PLL.

With reference to the DLL of FIG. 18B, many elements are identical tothe embodiment of FIG. 18A. However, the output of the low pass filter186 is sent to a control logic block 189, and the output of block 189forms the digital control bits that control the switching of the MOStransistors of transmission line 182. The output 190 forms thephase-locked output of the DLL.

The advantages of these architectures include:

Low power;No need of power-hungry high-speed frequency divider compared toconventional structures in high frequency circuits;High speed;Fast capturing and tracking time due to very short locking loop (nofrequency divider chain);Low spurs;Errors in frequency and phase are corrected in every cycle (no delaycaused by the long dividing chain in conventional structures);Large capturing/tracking range;DiCAD provides ultra wide of frequency tuning range.

DiCAD based SCO, SCPS, SCVI, SCRF and SCPLL/DLL are key building blocksto build software radio with reconfigurable, agile frequency hoppingcapability for multi-band and multi-mode communication systems.Advantages of the presently disclosed systems and methods include:

Ultra wide and linear tuning range on frequency, phase delay andcharacteristic impedance;Digitally controllable tuning range with very fine tuning step, suitablefor software radio implementation;Wide impedance tuning is particularly important for linear poweramplifier and wideband impedance matching.

On-chip DiCAD based SCOs, phase shifters, impedance matching networkhave been designed, simulated and implemented in silicon.

Digital controlled artificial dielectrics with wide tuning range onfrequency, phase delay and impedance are important for software radioimplementations. The DiCAD can be used to tune operating frequencies ofcomponents, such as resonators, antennas, filters, baluns, duplexers; totune phase delay in transmission lines; to shrink the size of inductorsand transformers. It can be inserted to circuits, such as amplifiers,mixers, filters, oscillators, PLLs/DLLs and any other circuits withlarge frequency, phase delay or impedance tuning requirements. Thedisclosed techniques and circuits are ideal for software radio buildingblock circuits.

Two different structures have been shown in FIGS. 9 and 11. FIG. 9 showsa differential structure, where a ground reference is not needed becauseof the virtual ground present in all differential structures. FIG. 11shows a non-differential structure in combination with a groundreference. The following examples of FIGS. 12A, 13, 14, 17A and 17B havebeen described with reference to the differential structure of FIG. 9.However, the person skilled in the art will understand, upon reading ofthe present disclosure, that the two structures of FIGS. 9 and 11 areinterchangeable therebetween, and that the examples of FIGS. 12A, 13,14, 17A and 17B could also be implemented with the structure shown inFIG. 11.

Further, with reference to the switch embodiments, while the presence ofMOS or CMOS switches is to be preferred, other kind of switches havingthree terminals or more can be used.

Therefore, in summary, according to one of the embodiments of thepresent disclosure, tuning devices and methods are disclosed. One of thedevices comprises a metal structure connected with artificial dielectricelements, and variable capacitance devices. Each variable capacitancedevice is connected with a respective artificial dielectric element andwith a control signal. Control of the variation of the capacitanceallows the desired tuning. Another device comprises metallic structuresconnected with artificial dielectric elements and switches connectedbetween the artificial dielectric elements. Turning ON and OFF theswitches allows the capacitance between artificial dielectric elementsto be varied and a signal guided by the metallic structures to be tuned.

While several illustrative embodiments of the invention have been shownand described, numerous variations and alternative embodiments willoccur to those skilled in the art. Such variations and alternativeembodiments are contemplated, and can be made without departing from thespirit and scope of the invention as defined in the appended claims.

1. A device comprising: a plurality of artificial dielectric elements; ametal structure coupled with the plurality of artificial dielectricelements; and a plurality of variable capacitance devices, each variablecapacitance device having a first end connected with a respectiveartificial dielectric element of the plurality of artificial dielectricelements, and a second end; wherein each second end is adapted to beconnected to a control signal, the control signal controlling variationof the capacitance of the variable capacitance devices.
 2. The device ofclaim 1, wherein the metal structure is adapted to carry a signal topolarize particles in the artificial dielectric elements.
 3. The deviceof claim 1, wherein the plurality of variable capacitance devicescomprises groups of variable capacitance devices, each variablecapacitance device of a same group having its second end adapted to beconnected to a same control signal.
 4. The device of claim 1, whereinthe artificial dielectric elements are floating metal sheets.
 5. Thedevice of claim 1, wherein the metal structure is a differentialstructure comprising a first branch and a second branch.
 6. The deviceof claim 1, wherein the metal structure is a single-ended structurecomprising a metal branch and a ground reference.
 7. The device of claim5, wherein the first branch and the second branch are short-circuited ata first end thereof and open-circuited at a second end thereof.
 8. Thedevice of claim 7, wherein the short-circuited first end is connectableto additional circuitry through current coupling and the open circuitedsecond end is connectable to additional circuitry through voltagecoupling.
 9. The device of claim 1, wherein the metal structure isU-shaped.
 10. The device of claim 1, said device being a voltagecontrolled oscillator, a frequency of the voltage controlled oscillatorbeing tuned by said control signal.
 11. A voltage controlled oscillatorcomprising: a metallic structure to guide an input wave; a plurality ofartificial dielectric elements connected with the metallic structure,the input wave polarizing metal particles in the artificial dielectricelements; and variable capacitance devices, each having a first endconnected with a respective artificial dielectric element, and a secondend adapted to be connected with a control signal, the second ends ofthe variable capacitance devices forming a control input of the voltagecontrolled oscillator to control the frequency of the input wave. 12.The voltage controlled oscillator of claim 11, wherein the metallicstructure is a differential structure comprising a first branch and asecond branch.
 13. The voltage controlled oscillator of claim 11,wherein the metallic structure is a single-ended structure comprising ametal branch and a ground reference.
 14. The voltage controlledoscillator of claim 12, wherein the first and the second branch areshort-circuited at a first end thereof and short-circuited at a secondend thereof.
 15. A method for tuning a signal, comprising: coupling ametal structure with a plurality of artificial dielectric elements, themetal structure adapted to guide the signal to be tuned; providing aplurality of variable capacitance devices, each variable capacitancedevice having a first end connected with a respective artificialdielectric element of the plurality of artificial dielectric elements,and a second end; connecting each second end to at least one controlsignal; and tuning the signal by varying the capacitance of the variablecapacitance devices through the at least one control signal.
 16. Themethod of claim 15, wherein the plurality of variable capacitancedevices comprises groups of variable capacitance devices, each variablecapacitance device of a same group having its second end connected to asame control signal.
 17. The method of claim 15, wherein the artificialdielectric elements are floating metal sheets.
 18. The method of claim15, wherein the metal structure comprises a first branch and a secondbranch.
 19. The method of claim 18, wherein the first branch and thesecond branch are short-circuited at a first end thereof andopen-circuited at a second end thereof.
 20. The method of claim 19,further comprising: connecting the short-circuited first end toadditional circuitry through current coupling.
 21. The method of claim19, further comprising: connecting the open-circuited second end toadditional circuitry through voltage coupling.
 22. The method of claim15, wherein said signal is tuned to control frequency of a voltagecontrolled oscillator.
 23. A device comprising: a first and a secondplurality of artificial dielectric elements; a first metallic structurecoupled with the first plurality of artificial dielectric elements; asecond metallic structure coupled with the second plurality ofartificial dielectric elements; and a plurality of switches, each switchconnected with a respective artificial dielectric element of the firstplurality of artificial dielectric elements and a respective artificialdielectric element of the second plurality of artificial dielectricelements, each switch further connectable with a control signal, thecontrol signal tuning the frequency of a signal guided by the first andsecond metallic structures.
 24. The device of claim 23, wherein eachswitch is a metal oxide semiconductor (MOS) switch having a gate, asource and a drain, the gate being connectable with the control signal,the source being connected with the respective artificial dielectricelement of the first plurality of artificial dielectric elements, andthe drain being connected with the respective artificial dielectricelement of the second plurality of artificial dielectric elements. 25.The device of claim 23, wherein the control signal is adapted to switcheach switch between a first state where a first capacitance isestablished between the respective artificial dielectric elementsconnected with the switch and a second state where a second capacitance,different from the first capacitance, is established between therespective artificial dielectric elements connected with the switch. 26.A switch controlled oscillator (SCO) comprising the device of claim 23.27. The SCO of claim 26, wherein the first and second metallicstructures are short-circuited at one end thereof and open-circuited atthe other end thereof.
 28. The SCO of claim 27, further comprising anexcitation network providing a negative resistance effect, theexcitation network connected to the open-circuit end of the first andsecond metallic structures.
 29. A resonator comprising a plurality ofdevices in accordance with claim 23, said devices being connected in aclosed loop arrangement, wherein in each device the first and secondmetallic structures are connected to a negative resistance arrangementat both ends.
 30. The resonator of claim 29, wherein the plurality ofdevices are four devices.
 31. A transmission line, comprising the deviceof claim 23, wherein the first and second metallic structures have afirst end and a second end, the first ends of the first and secondmetallic structures forming an input of the transmission line, and thesecond ends of the first and second metallic structures forming anoutput of the transmission line.
 32. A switch controlled reconfigurablefilter comprising the device of claim 23, wherein length of an ON periodand length of an OFF period of the switches are controllable.
 33. Adevice comprising: a plurality of artificial dielectric elements; ametallic structure coupled with the plurality of artificial dielectricelements; a plurality of switches, each switch having a first terminalconnected with a respective artificial dielectric element of theplurality of artificial dielectric elements, a second terminal connectedwith ground, and a third terminal connectable with a control signal, thecontrol signal tuning the frequency of a signal guided by the metallicstructure.
 34. The device of claim 33, wherein the switch is a metaloxide semiconductor (MOS switch), the first, second and third terminalsbeing the drain, source and gate of the MOS switch, respectively.
 35. Aswitch controlled oscillator (SCO) comprising the device of claim 33.36. A resonator comprising a plurality of devices in accordance withclaim 33, said devices being connected in a closed loop arrangement. 37.A transmission line comprising the device of claim
 33. 38. A switchcontrolled reconfigurable filter comprising the device of claim
 33. 39.A synthesizer comprising: a voltage control oscillator (VCO), atransmission line connected to the VCO, the transmission line having atransmission line input and a transmission line output; a mixer adaptedto mix a signal on the transmission line input with a signal on thetransmission line output, the mixer having a mixer output; and a lowpass filter connected with the mixer output, the low pass filter havinga low pass filter output connected with the VCO, wherein thetransmission line is a transmission line in accordance with claim 31.40. The synthesizer of claim 39, said synthesizer being a phase lockedloop (PLL) device.
 41. The synthesizer of claim 39, further comprising acharge pump connected between the low pass filter and the VCO.
 42. Thesynthesizer of claim 39, wherein the VCO comprises a device inaccordance claim
 23. 43. The synthesizer of claim 39, wherein the VCOcomprises a device in accordance with claim
 33. 44. A delay locked loop(DLL) device comprising: a voltage control oscillator (VCO); atransmission line connected to the VCO, the transmission line having atransmission line input and a transmission line output; a mixer adaptedto mix a signal on the transmission line input with a signal on thetransmission line output, the mixer having a mixer output; a low passfilter connected with the mixer output, the low pass filter having a lowpass filter output; a control logic block connected with the low passfilter output, the control logic block having a control logic blockoutput; wherein the transmission line is a transmission line inaccordance with claim
 31. 45. A synthesizer comprising: a voltagecontrol oscillator (VCO); a transmission line connected to the VCO, thetransmission line having a transmission line input and a transmissionline output; a mixer adapted to mix a signal on the transmission lineinput with a signal on the transmission line output, the mixer having amixer output; and a low pass filter connected with the mixer output, thelow pass filter having a low pass filter output connected with the VCO,wherein the transmission line is a transmission line in accordance withclaim
 37. 46. The synthesizer of claim 45, said synthesizer being aphase locked loop (PLL) device.
 47. The synthesizer of claim 45, furthercomprising a charge pump connected between the low pass filter and theVCO.
 48. The synthesizer of claim 45, wherein the VCO comprises a devicein accordance with claim
 23. 49. The synthesizer of claim 45, whereinthe VCO comprises a device in accordance with claim
 33. 50. A delaylocked loop (DLL) device comprising: a voltage control oscillator (VCO);a transmission line connected to the VCO, the transmission line having atransmission line input and a transmission line output; a mixer adaptedto mix a signal on the transmission line input with a signal on thetransmission line output, the mixer having a mixer output; a low passfilter connected with the mixer output, the low pass filter having a lowpass filter output; a control logic block connected with the low passfilter output, the control logic block having a control logic blockoutput; wherein the transmission line is a transmission line inaccordance with claim 37.